Centrifugal pump



-July 2s, 1942. c. BLOM 2,291,135

GENTRIFUGAL PULP 1 Y Filed YJam. 5'. 1959 2 sheets-sheet 1 Patented July284, 1942 d CENTRIFUGAL PUMP Carl Blom, Portland, Oreg., assigner toBingham Pumpl Company, Inc., Portland, Oreg., a corporation of Oregonappueauonsanuary 5, 1939, serm1No.249,4s1

claims. (01.103-113) This invention rentes to liquid pumps of' thecentrifugal type, and has particular reference to an improvedconstruction for relieving such pumps of air or other gases which may beentrained with the liquid during pumping operations, or for exhaustingair or other gases from the intake pipe to lift liquid to the pump.

It is' an object of the invention to provide a liquid pump of thecentrifugal type which will continuously and eiiiciently pump pulp andother liquids which contain entrained air or free gases. It is a furtherobject of the invention to provide a liquid pump of the centrifugal typehaving means for exhausting from said pump the air and gases entrainedwith the liquid being pumped.V

It is a further object of the invention to provide a liquid pump of thecentrifugal type which will expel air and gases from the pump wheneverthe air and gases entrained in the liquid being pumped are of sufficientquantity to accumulate in or adjacent the eye of the impeller.

It is a further object of the invention to provide a centrifugal pumpwhich, when partially filled with liquid, will exhaust air and gasesfrom the intake pipe to lift liquid to the pump.

With these and other objects in view, the invention resides in the novelconstruction and combination of parts hereinafter described, illustratedin'the accompanying drawings, and set forth in the appended claims;itbeing understood that various changes in form, proportion, size anddetails of construction within the scope of the claims may be resortedto without departing from the spirit or sacrificing any of theadvantages of the invention.

In the drawings:

Figure 1 is a side elevation, partly in section, of a verticallypositioned pump embodying the presi ent invention.

Figure 2 is a horizontal section taken on the line 2-2 of Figure 1 andillustrating the sectors of the pump casing and their relation to theother parts of the pump.

- Figure 3 illustrates a modified construction of the pump casingillustrated inFigure 2.

Figure 4 is a side elevation, partly in section, of a horizontallypositioned pump which is a modification of the pump shown in Figure 1.

Figure 5 is a fragmentary side elevation of the Dump shown in Figure 1,excepting that the construction illustrated does not embody an air ventor air vent port shields.

Figure 6 is a horizontal section taken on the line 6-6 ofFigure 5.

of the casing shown in Figure 3 as the same would appear if taken on theline 6--6 of Figure 5.

' Referring to the drawings, an embodiment of v the improved pump may beeither as illustrated in Figure l or in Figure 4. Figure l illustrates avertical type pump, while Figure 4 illustrates a horizontal type pump.The structural differences between the pumps illustrated in the twofigures are only as affect-the operability vof the pump in therespective positions. The principle of the invention is the same in bothtypes.

The pump illustrated in Figure 1 comprises a vertical shaft I which isJournalled in a lower bearing 2 and an upper bearing 3. The lowerbearing 2 is housed in a bearing housing 4 which is supported upon abracket or pedestal 5. Power to drive the shaft l is supplied by a motor6 disposed 'above and in vertical alignment therewith, the pump shaftand motor being connected by a coupling l.

An impeller 8 is affixed to the shaft I as by a key 9 so as to rotatetherewith, and is held in axial position by a shaft sleeve I0 andimpeller nut Il threaded on the shaft. The impeller 8 is housed in apump casing comprising side plates whence it passes through the eye ofthe impeller` and through passages defined by the impeller vanes i6 andintothe area defined by the volute '|4. The liquid is discharged fromthe pump .volute through the discharge port Il.

It is well known that pulp and other liquids have air and free gasescontained therein, and that when acted upon by a centrifugal pumpimpellerthe air and gases entrained with the liquid often accumulateswithin the pump near the center of the rotating body of liquid inquantities sufiicient to interfere materially with the flow of liquidtherethrough. In a centrifugal pump of ordinary construction, air andgases which accumulate in the impeller passages during operation of thepump are not acted upon by the ow of liquid through the volute casing.In such a Ipump the area of the volute casing-increases in the directionof iiow and, under normal operating conditions, the liquid' velocity andpressure are approximately constant throughout the area of the volute;there being a continuous outow of liquid through the impeller passagesexcepting at such times as air and gases accumulate therein in Figure 7illustrates the modified construction 55 suilicient quantities tointerfere with the normal operation of the pump. To overcome thisdifficulty, applicant has provided a centrifugal pump having an air ventport I9 positioned in or adjacent the eye of the impeller, and a pumpcasing having its inside periphery divided into sectors, lthearrangement of said sectors causing a reversal of flow of liquidcontained in the passages between adjacent impeller vanes at a pointadjacent the air vent forcibly discharging accumulated air and gasesfrom the pump through said port.

Referring to Figures 2 and 3 of the drawings, the casing of a pumpembodying the invention is disclosed as having three sectors, which aredefined as being from A to B, from B to C, and from C to D. The sector Cto D of the pump casing functions normally as in a conventionalcentrifugal pump, in which there is a continuous outflow of liquidthrough the impeller passages into the volute casing. Consequently, airand gases which accumulate in the impeller passages during that part ofthe rotative cycle where they are in registry with the sector C to D ofapplicants pump are not acted upon by the ow of liquid through thevolute casing. y

Referring to Figure'2, the sector of the pump casing defined as from Ato B the area ofthe pressure chamber or volute is progressivelydecreased by the convergence of the casing wall with respect to theperiphery of the impeller 8. As the liquid follows the impeller, aportion of the liquid in the pump casing is forced to reenter theimpeller passages on account of the convergence of the casing wall,causing a momentary reversal of ilow in the impeller passages while theyare in that part of the cycle of rotation adjacent the sector A to B. Anair vent port Il is positioned to register with the inner ends of theimpeller passages at the moment oi' maximum compression of theaccumulated air and gases caused by the reversal of ow of liquidtherewithin, and to provide egress from the pump for such accumulatedair and gases, there is provided an air vent pipe I8. It will be notedthat the air vent pipe I8 is equipped with shield portions 20 and 2|extending laterally from each side thereof, the pipe I8 and shieldportions 20 and 2| serving to close of! the ,inner ends of the impellerpassages during rotation of the impeller through the sectors A to B andB to C from the impeller eye. Section 20 of the shield extends from theair vent port in a direction opposed to the rotation of the impeller,and `section 2| of the shield extends from the air vent port in thedirection of rotation of the impeller. The width of the section 2l ofthe shield may be modified according to conditions under which t'ne pumpis required to operate. It will be noted that the air vent pipe Il andshield 2li-2l form a continuous closure for the inner ends of theimpeller passages during rotation. thereof through the sectors A to Band B to C, which closure serves to cut o1! the outflow of liquid fromthe impeller :ge through the impeller passages in these sec- As the flowof liquid is reversed in the impeller passages in the sector A to B, theair and gases therewithin are trapped in the impeller passages by thesection 20 of the shield, and prevented from escaping back into the eyeof the impeller. As rotation of the impeller brings` the respectiveinner ends of the passages into registry with the air vent port Il, theair and gases are permitted to escape therefrom through the air vent Iland through the air vent pipe 22, the latter terminating within the areaof the suction li as illustrated in Figure 1, or at a point remote fromthe pump, as may be desired.

The sector defined as from B t0 C is that p0rltion of the'insideperiphery of the pump casing are out of registry with the air vent port,to prevent air being drawn into the passages through the air vent portwhen the liquid in the passages again begins its normal outward flow.

Referring now to Figure 3, there is illustrated a modiiled constructionof the pump casing, the construction differing from that illustrated inFigure 2 only in the contour of the peripheral wall of the casing. Inthe modified construction the point A of the wall which forms the inwardend of the liquid discharge port I1 is extended and curved inwardlytoward the impeller 8. 'Ihis construction forms a lobe 22 in the pumpcasing, and during rotation of the impeller the liquid is momentarilydrawn outwardly from the impeller passages before being forced into thepassages by the convergence of the casing wall and the impeller, ashereinabove described.

The outward movement of the liquid from the impeller passages, under theinfluence of the divergence of the casing wall from the impeller, causesa displacing effect at the inner end of the impeller passages whichpositively draws air into the passages from the eye of the impeller.Thus any air which has accumulated in the eye of the -impeller ispositively'drawn into the passages prior to the compressing anddischarging action of the liquid under iniluence of the converging wallof the pump casing. The inner ends of the impeller passages are closedby the air vent shield 20 as the liquid is forced into the passages bythe convergence of the casing wall, whereupon the air is firstcompressed and then exhausted from the pump through the air vent port I9in the same manner as hereinbefore described.

In Figures 5, 6 and 'I is illustrated a pump and a modification thereofsimilar to the construction illustrated in Figures 1, 2 and 3,-exceptingthat the pump does not embody an air vent pipe or air vent port shields.Under certain operating conditions the presence of the air vent and airvent port lshields is necessary. 'I'hese elements form a valve which isfirst closed to c'ause the air and gases to be compressed, then openedto premit the air and gases to escape, and thereupon closed to preventair being drawn into the pump therethrough. The pump illustrated inFigures 1 and 5 is a vertical pump of the type devised for handling pulpand foamy liquids. In such pumps the liquid enters the suction chamberI5 A the valve structure is unnecessary. Under such ing gland 28.

impeller into the atmosphere in the upper portion of the suctionchamber.

The pump illustrated in Figure 4 comprises a motor 23 having a shaft 24which drives an impeller 25. The shaftis journalled in a bearing 26which includes the usual packing 21 and pack- The impeller is secured tothe shaft by means of a machine screw 29 and key 3B. The pump casing isformed by a volute 3i and a suction plate 32, the latteralso definingthe walls of the intake port 33. The pump casing embodies sectors A toB, B to C, and C to D, as shown in Figure 2, and is equipped with an airvent port 34 and air vent port shield 35 as hereinbefore described inconnection with the pump illustrated in Figure 1. The operation of thepump is identical with the operation of the pump shown in Figure 1; andthe functions of. the respective sectors .of the pump casing and theirrelation to the impeller passages, air vent and air vent shield are alsoas hereinbefore described. The horizontal type 4pump may also bedesigned for operation under low suction head, and wheneverthiscondition prevails the pump may be constructed and successfullyoperated without the use of an air vent port or air vent port shield.

This application is a continuation in part of my application Serial No.117,165, filed December 22, 1936, for Centrifugal pump. f A

Having now described my invention and in' what manner the same may beused, what I claim as new and desire to protect by Letters Patent is:

1. A centrifugal pump designed to exhaust the air and gases entrainedwith the liquid being pumped, comprising a casing having a dischargeopening, an impeller rotatively mounted within said casing, saidimpeller having passages defined by a plurality of vanes extendingoutwardly from the eye ofthe impeller, said casing closely approachingsaid impeller at a point adjacent one side of said discharge opening,said casing in a sector beyond said'point first diverging from saidimpeller to draw air and gases from the eye of the impeller into saidimpeller passages and then converging on said impeller for momentarilyreversing the flow of liquid inthe impeller passages to exhaustentrained air and gases,r then, beyond said sector, again diverging fromsaid impeller in a volute Aextending to the other side of said dischargeopening, a shield for closing the inner ends of said impeller passagesduring their travel past a portion of said sector for entrapping air andgases in said impeller passages. and an air vent port adjacent theconvergent portion of the casing and communicating with the inner endsof the impeller passages for venting said impeller passages during saidperiod of momentary reversal of i'low of liquid therein. l

2.l A centrifugal pump of the type comprising a generally volute casing.an impeller rotatively mounted within said casing, an inlet for saidpump communicating with the leye of the impeller, said impeller havingpassages defined by a plurality of vanes extending outwardly fromtheliquid from said impeller passages and then to forceL liquid into theimpeller passages from the pump lcasing, and an air vent port adjacentthe convergent portion of the casing and communieating with the innerends of the impeller passages for venting the impeller 'passages at thetime liquid is caused to enter said passages from the casing, saidcasing beyond said convergence continuing in a diverging voluteextending around to the opposite side of said discharge port.

3. A centrifugal pump of the type comprising a generally volute casing,a discharge port in said casing, an impeller rotatively mounted withinsaid casing, saidimpeller having vpassages dened by a plurality of vanesextending outwardly from the eye of the impeller, means for exhausts ingfrom said pump the air and gases entrained with the liquid being pumped,said means com- 1 prising a sector of said casing adjacent one side ofthe`inner end of the discharge port which first diverges from theimpeller to positivelydraw air and gases from the eye of the impellerinto said impeller passages and then converges with respect to theperiphery of the impeller formomentarily reversing the flow of liquid inthe ixnpeller passages during rotation of the impeller through vsaidsector for ejecting air and gases from said passages, and an air ventport adjacent the convergent portion of the casing and communicatingwith the inner ends of the impeller passages to receive air exhaustedfrom 'said passages, during said momentary reversal of iiow of liquid insaid passages.

4. A centrifugal pump of the type comprising a generally volute casing,a discharge port in said casing, an impeller rotatively mountedwithinsaidfcasing, said impeller having passages dened by a plurality of vanesextending outwardly from the eye of the impeller, means for exhausteyeof the impeller, a discharge port for said cassector, said sectoroperating nrstto withdraw ing from said pump the air and gases entrainedwith the liquid being pumped, said means comprising a sector of saidcasing adjacent one side 4 of the inner end of the discharge port whichfirst diverges from the impeller to positively draw air and gases fromthe eye of the impeller into said impeller passages and then convergeswith respect to the periphery of the impeller' for momentarily reversingthe ow of liquid in the impeller, passages during rotation of theimpeller through said sector for ejecting air and'gases.

from said passages.

5. A centrifugal pump of the type comprising a' generally volute casing,an impeller rotatively mounted within saidcaSing, said impeller havingpassages defined by a plurality .of vanes extending outwardly from theeye of the impeller, an

inlet chamber for receiving material to be pumped and for introducingsaid material into the eye of the impeller under gravity head, means forexhausting from said pumpthe air and gases entrained with the liquidbeing pumped, said means consisting of a sector of said casing whichconverges with respect to the periphery of the impeller for momentarilyreversing the now of liquidin the impeller passages'during rotation ofthe impeller through said sector for ejecting air and gases from saidpassages, the inner ends' of substantially all of said impeller passagesbeing open for the intake of liquid to be pumped. the ejected air andgases being caused to escape to the atmosphere above the surface of theinowing liquid approaching the eye of the impeller.

CARL BLOM.

